The present application is based on Japanese Patent Application No. 2000-395903, which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to an automobile interior member with an air bag cover portion to which an air bag device is assembled, such as an instrument panel, a door trim, a seat back, and the like.
Here, description will be made mainly on an instrument panel by way of example, but the present invention is not limited thereto.
If no particular definition is specified in the specification, the front, rear, right and left of an automobile interior member (instrument panel) are defined correspondingly to the front, rear, right and left of a real automobile on which the automobile interior member is mounted.
2. Description of the Related Art
In the background art, an instrument panel of this kind was constituted by a main body portion, and a bag cover portion which was provided with a mounting foot portion for mounting the bag cover portion on an air bag casing. The main body portion and the bag cover portion were molded separately and then assembled integrally in a post-process so as to form the instrument panel.
However, in the conventional method, a mold can not utilized in common, and man-hours for molding and man-hours for assembling are increased.
In order to solve the above-mentioned problems, for example, a variety of members formed by dichromatic molding have been proposed as follows (in JP-A-9-2188, JP-A-11-91484 and the like).
After a main body portion is injection-molded (primarily molded) out of rigid plastic material (first thermoplastic resin material) such as PP-F (fiber reinforced polypropylene) or the like, a bag cover portion is injection-molded (secondarily molded) out of flexible plastic material (second thermoplastic resin material) such as TPO (olefin type thermoplastic elastomer) or the like, by use of one and the same mold as that for the main body portion, so that the main body molded portion and the bag cover portion are welded integrally with each other.
Generally, in view of the breakage property of a tear line (breakage line), the tear line serving as a portion for partitioning a lid portion of the bag cover is constituted by a main groove portion formed in the inside and a sub-groove portion (relief line) formed in the outside.
Recently, with respect to design performance, a so-called relief-lineless type, where the tear line (breakage line) serving as the portion for partitioning the lid portion does not appear on the surface (design surface) side namely the relief line is not formed in the surface side, is strongly demanded.
However, when the relief-lineless request was to be fulfilled, an extra number of man-hour such as post-processing or the like was required for obtaining predetermined breakage load properties (tear property) of the tear line (breakage line).
In consideration of the above-mentioned problems, an object of the present invention is to provide an automobile interior member with an air bag cover portion such as an instrument panel or the like, in which predetermined breakage load properties can be obtained easily, and making relief-lineless in the air bag cover portion can be made easily without taking any special measure such as post-machining or the like on the tear line.
In order to solve the problems as described above, as a result of making every endeavor to eagerly develop a new interior member, the inventors have conceived an automobile interior member with an air bag cover portion in the following configuration.
That is, an automobile interior member with an air bag cover portion, in which an air bag device is to be mounted, is constituted by a main body portion and the air bag cover portion, the main body portion and the air bag cover portion being formed in a manner so that the main body portion is formed out of a first thermoplastic resin, and the air bag cover portion is formed out of a second thermoplastic resin so as to be welded integrally with the main body portion; wherein the second plastic resin is oriented in a direction along a tear line portion(a main breakage line: a end edge of a rotational lid portion) serving as the end edge of the lid portion in the air bag cover portion so that the air bag cover portion is formed.
More specifically, an automobile interior member with an air bag cover portion, to which an air bag device is assembled, is constituted by a main body portion and the air bag cover portion, the main body portion and the air bag cover portion being formed by molding in a manner so that the main body portion is primarily molded out of a first thermoplastic resin, and the air bag cover portion is secondarily molded so as to be welded integrally with the main body portion; wherein a gate portion of the air bag cover portion is positioned in a direction so that the gate portion intersects a tear line portion (a end edge of a rotational lid portion) serving as the end edge of the lid portion; and wherein a guide rib for guiding material flow from the gate portion in a direction along the tear line portion is formed on a back surface of the air bag cover portion.
In the bag cover portion of the automobile interior member with the air bag cover portion such as an instrument panel or the like, the material flow is oriented along the tear line portion, in the same manner as that in the above configuration. As a result, the inventors have discovered a fact that predetermined breakage load properties can be obtained easily, and making relief-lineless can be made easily without taking any special measure such as post-machining or the like on the tear line.
It is supposed that the load for opening the lid portion at a moment when an air bag is operated depends mainly on the breakage property (breakage load) of the tear line portion that serves as a breakage start portion (initial breakage portion).
That is, after the initial breakage portion (tearing start portion: slit) has been formed at a portion of the tear line portion by the expansion and deployment pressure of the air bag, the tearing (breakage) proceeds from the initial breakage portion as the start point to thin-walled portions (the tear line portion and sub-tear lines that constitute the edges of the lid portion on the opposite sides), so that the lid portion is opened. The tearing load for making the tearing proceed may be considerably lower than the breakage load (tearing load) for forming the initial breakage portion (tearing start portion).
Accordingly, it is supposed that even when the material flow in the bag cover portion is positioned in a direction so that the material flow intersects the sub-tear lines, no problem occurs in the breakage property (separating property: tear property).
In the above-mentioned configuration, the guide rib is generally formed (1) in a mode in which the guide rib is disposed to extend from a position where the gate portion is located to a position of an end of the tear line portion (a position corresponding to the arrangement of the tear line portion), or (2) in a mode in which the guide rib is disposed to extend from a position of the gate portion to a position beyond the position of the end of the tear line portion (corresponding to the arrangement of the tear line portion), so that openings are formed in the symmetrical positions with respect to the tear line portion.
Further, in each of the modes described above, a hook portion is preferably formed at the top end of the guide rib for the following reasons. That is, the flow direction of the material can be easily controlled, and in the case of the mode (1), a phase difference in the material flow is generated on the tear line due to the existence of the hook portion to thereby bring more improvement in the breakage property.
Furthermore, when reliable tearing of the breakage line for opening is required, the basic idea of the automobile interior member with an air bag cover portion according to the present invention is also applicable to an injection-molded article which includes a first portion as main body of the injection-molded article and a second portion having a tear line for opening, the second portion being broken at a predetermined load so as to form an opening portion in an inside of the first portion; wherein the injection-molded article is formed in a manner so that the first portion of the injection-molded article is primarily molded out of a first thermoplastic resin, and the second portion is secondarily molded so as to be welded integrally with the first portion; and wherein molding material flow is directed in a direction along the tear line for the opening portion in the second portion so that the second portion is secondarily molded.